1. Field of the Invention
This invention relates generally to the field of suspension systems, and more particularly, but not by way of limitation, to a squatdown axle and suspension system for vehicles used to haul cargo. The squatdown suspension system includes an adjustable squatdown axle so that the cargo bed can be lowered to the loading surface to achieve a load angle of as little as 3 degrees.
2. Discussion
In the past, tow trucks utilized tow bars, dollies, or slings to tow vehicles from one location to another. The tow truck of the past has been replaced by a truck capable of hauling the vehicle instead of towing the vehicle. The improved design, referred to herein as a rollback design, includes a cargo bed which rolls back on a frame from a transport position to a load position. In the load position, the rear of the cargo bed is lowered to the road surface while the front of the cargo bed remains elevated. The rollback design includes a winch (with cable) attached to the front of the frame. The cable is attached to the vehicle which is to be hauled, the winch pulls the vehicle into position on the cargo bed, and the vehicle and rollback cargo bed are then pulled forward to a level hauling position. Tie downs, chains, and the like are used to secure the transported vehicle to the cargo bed.
The rollback design discussed above, while an improvement over prior tow truck designs, includes several limitations. Rolling the cargo bed back to permit loading of a vehicle extends the overall length of the truck plus cargo bed so that some locations are inaccessible. Hauled vehicles having a low suspension, frame, or body are susceptible to damage from the cable due to the angle formed between the cargo bed and the loading surface when the cargo bed is in the load position. In the transport position, the cargo bed is typically a minimum of forty to forty-eight inches above the road surface, thus producing a high center of gravity during transport.
Conventional rental trucks and trailers used to haul household goods likewise require a raised dock or a ramp to permit loading of heavy items. U-Haul rental trucks, for example, are normally equipped with a slide-out ramp. Refrigerators, washers, dryers, and the like are typically loaded onto a hand truck, and the hand truck is pushed from the loading surface, up the ramp, into the cargo area of the rental truck. The slide-out ramp, like the rollback cargo bed, imposes space restrictions on the loading process. The process of moving heavy objects up the ramp introduces a risk of injury both to the items being moved and to personnel responsible for loading the heavy objects.
Some rental trucks, freight delivery trucks, and trailers are equipped with power lifts designed to lift heavy objects from the loading surface to the level of the cargo area. While the power lifts eliminate the need for moving personnel to push heavy objects up a ramp, the small size of the power lift creates additional safety concerns when personnel attempt to move heavy objects from the power lift into the cargo area.
Conventional livestock trailers used to haul horses, cattle, swine, and sheep face similar limitations. Livestock trailers may include a back door which can be lowered to form a loading ramp. The presence of livestock on the loading ramp can cause the trailer to become unstable during loading. With or without a loading ramp, the risk of injury to livestock and wranglers is greatest during loading operations. Trailers which are not equipped with loading ramps carry an increased risk of injury.
Available trucks and trailers for hauling cargo do not provide a suspension which permits the cargo bed to drop to the ground to permit loading of cargo, including automobiles, furniture, and other heavy objects, without use of ramps or docks.